Other Suggestions?

[Overclocked]

This Time, Im building Some Lights To Light up My desk while I work, because I have this lamp is just a bit annoying. Im going to use white LEDs that I got a while ago from Ebay. Their a bit silverish, but they will do fine in lighting up what I want to light up. I dont really need that much of a wide angle either, So Normal 5mm LEDs will do Fine. Here are my requirements thusfar,

Vin = 1.5 to infinite (or some large value, doesnt matter)
Vout = 28V
Iout = 160 mA

IC Chosen: LT1618
https://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1094,C1766,P2079

LED strings will consist of the following; 8 in series with another 8 in parallel, which totals 16 LEDs. Total Current Per LED Lamp = 40mA (assuming 20mA Per String). Total Voltage = 28V (assuming 3.5V Per LED). There will be 4 LED Lamps, which brings my total current requirement up to 160mA.

Note: A LED Lamp is what will contain the 16 LEDs...made out of PVC.

Now it seems that there now is a rather large number of Boost Converters That Seem to Fit the picture, and because of that, Does anyone else Have any other IC's they have in Mind? Err Anything "better" per say. I know theres a whole crap load of boost converters out there, it was kinda hard choosing one, But I chose this one because of Ease of Use, Size, and Linearity of Efficiency.

One requirement though, Cannot Be QFTN or QFN Or Any other of those weird packages (they are square and have pads Underneath that a normal soldering iron cannot get too) . Can be SOIC, MSOP, SOP...etc. Can be Either SMD or Through hole.

 

[audioguru]

You forgot to include a current regulator and extra voltage for it.
You are ASSUMING 3.5V per LED. They have a range of voltages and might all be 3.2V then without something to limit the current they will BLOW UP!
If they are all 3.8V then none will light with 28V.

Your requirement is 28V x 160mA= 4.48W. Plus more for the current-limiter.
If your source voltage is only 1.5V (it will begin to drop immediately) then its current is more than 4.48W/1.5V= 3A! A pretty big battery is needed. You will see the LEDs dim as the battery runs down.

 

[Overclocked]

You forgot to include a current regulator and extra voltage for it.
You are ASSUMING 3.5V per LED. They have a range of voltages and might all be 3.2V then without something to limit the current they will BLOW UP!
If they are all 3.8V then none will light with 28V.

Your requirement is 28V x 160mA= 4.48W. Plus more for the current-limiter.
If your source voltage is only 1.5V (it will begin to drop immediately) then its current is more than 4.48W/1.5V= 3A! A pretty big battery is needed. You will see the LEDs dim as the battery runs down.

Opps! Your right, forgot that thing!

My Fault again, Im not going to run on 1.5V, but its nice to know it will run on 1.5V. Im thinking more like 4.5 to 6V (3 or 4 AA's or D cell batteries). I was also going to run it off of a DC Powersupply for when I dont need batteries. The batteries are just there as backup. This wasnt going to be part of my original plan, but it makes more sense to have Practically infinite power available than to run it off batteries.

The Reg I chose can run up to 18V, and I know I have some 9V Wall warts I could hack into. I'll have to look around to see what I can find. The only thing Im worried about is noise caused by the Switching reg, I guess I could still keep things simple and use a small cap to filter out the 1.6Mhz Noise.

Offline would be too complicated for me at this point. I understand all the building blocks involved, its just I want to KISS.

ADD: If Need Be, The reg can go up to 35V.

 

[Gordz]

Before you decide, why not have a look at some of these products ?
**broken link removed**

 

[Overclocked]

Before you decide, why not have a look at some of these products ?
**broken link removed**

I have, the problem is a physical limitation, ie the package. Ive looked at the datasheet, and its a QFN Package.

 

[Gordz]

QFN are not too bad to solder, it is the BGA packs that are 'impossible'. What about the TPS61040/1 devices on that page ? SOT-23-5 is OK and I have used these before or are you looking for a 'single chip' solution rather ?

 

[Overclocked]

QFN are not too bad to solder, it is the BGA packs that are 'impossible'. What about the TPS61040/1 devices on that page ? SOT-23-5 is OK and I have used these before or are you looking for a 'single chip' solution rather ?

How So?

**broken link removed**

The package Im talking about is circled in green. My tip is bigger than the pins on the thing! This is a TI Part, QFN-10 Package. Impossible to solder unless I use a oven of some sort. Even then, I dont know if the traces can be that small!

SOT-23-5 Is ok. Thanks for the suggestion, I'll compare the two (or more) later on

 

[Gordz]

I use an Antex soldering iron with .5mm tip for SMD work. If you are doing anything with SOT-23 style packs you may consider getting a more suitable soldering iron and tip, You will then be able to do QFN

 

[Overclocked]

I use an Antex soldering iron with .5mm tip for SMD work. If you are doing anything with SOT-23 style packs you may consider getting a more suitable soldering iron and tip, You will then be able to do QFN

Funny thing is, I had to "mod" my tip to make it smaller, I pretty much used a bench grinder and a drill the turn it so it would be equal on all sides. unfortunately Radio shack no longer sells the tips I need, So I was really planning on getting a new soldering Iron Soon (along with a new meter..)

 

[Gordz]

Funny thing is, I had to "mod" my tip to make it smaller

I have done that once or twice in a pinch but it is not worth it. If you are in to electronics you really have to have a decent soldering iron and solder.

 

[Nigel Goodwin]

I have done that once or twice in a pinch but it is not worth it. If you are in to electronics you really have to have a decent soldering iron and solder.

And with any remotely modern tip it destroys the tip anyway, I've not seen an un-plated tip for 30 years or so?.

 

[Gordz]

Well.. it depends on the price range but yes, it's been a long time since I've seen an unplated tip. I like Antex because you just pop on whatever tip you need for the job, but they have a spiral wound heating coil on a ceramic element and I have 'lost' a few from dropping them off the bench on to the workshop floor. I then have an Oryx for the 'beefier' jobs.

 

[Hero999]

You've got 8 parallel strings of 8 in series which makes 64 in my book not 16.

I would stick them all in parallel and run them from fou or morer D cells with a step down constant current converter which will be far more efficient than using a boost converter and a power wasting series resistor.

 

[Overclocked]

For each Light it is 16 LEDs In total. For all four lights It is 64 LEDs.